Cyber Monday was the heaviest online spending day ever. Cyber Week brought in $6 billion — a record. And there were three days that week that eclipsed a billion dollars in spending. Bottom line: The online holiday shopping season has been a success so far.

Acccording to comScore, a site that tracks online spending, the week that began with Cyber Monday saw a 15% spike in sales, from $5.1 billion last year to almost $6 billion this year. And in the first 32 days of the November to December shopping season, $18.7 billion had already been spent online, with Cyber Monday itself bringing in $1.25 billion.

But it’s no wonder. E-tailers like Amazon, which is continuing to unveil holiday deals (see Amazon’s latest Flurry Deals), offered all sorts of heavy discounts and incentives to get shoppers to do much of their holiday spending online.

Another reason spending has surged this year was the prevalence of free shipping, something that seemed more like a perk in years past but is now virtually the norm. More than half of all transactions have included free shipping so far, and during Cyber Week, almost two-thirds included shipping at no cost.

As free shipping has become more common, it’s also now more of a priority for shoppers according to comScore. Almost 80% of consumers told the site that free shipping was either very or somewhat important to them when making purchases online this holiday season.

It’s difficult to determine whether the rise in online consumer spending is a sign that the economic recovery is picking up steam. We certainly seem to feel a bit more confident that we can spend more than last year. But at the same time, we’re again using credit cards for much of that spending.

Most likely, it’s been the over-the-top deals that brought consumers to spend in record numbers. But with such a strong start to the shopping season this year, it’s likely that spending will go down as we head toward the holidays.